Overloading and brake failure caused an accident that left 11 dead and 31 injured in northwest China's Ningxia Hui Autonomous Region on Saturday, local police said in a statement Monday.

The 19-seat mini-bus was carrying 42 people when its brakes failed. It then veered off the road and plunged into a ravine in Haiyuan County.

The operation of the Mingli Public Transport Co. mini-bus had been proscribed because the bus had failed to meet maintenance standards, the police statement said, and so the mini-bus's driver -- who was killed in the accident -- was operating the bus illegally when it crashed.

The injured are being treated in local hospitals and two are still in critical conditions.